Preparation of crosslinked cotton textiles



United States Patent 3,498,739 PREPARATION OF CROSSLINKED COTTON TEXTILES Alton L. Murphy and Clark M. Welch, New Orleans, and Matthew F. Margavio and Albert S. Cooper, Jr., Metairie, La., assiguors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Jan. 18, 1965, Ser. No. 426,452

Int. Cl. D06p 1/02 US. Cl. 8-125 10 Claims ABSTRACT OF THE DISCLOSURE The invention provides a method of preparing crosslinked and wash-wear resin-finished cotton fabrics having a tearing and breaking strength essentially the same as that of untreated native cotton fabrics, and an extensibility higher than that of crosslinked and wash-wear resin-finished native cotton fabrics. These improvements are accomplished by pretreating the yarn prior to weaving the fabric and subsequent wash-wear finishing of said fabric. The yarn pretreatment comprises shrinking the yarn by soaking it without tension in 10-30% by weight aqueous sodium hydroxide at temperatures about from -3 to 30 0, followed by stretching the alkali-wet yam to about 90-105% of the original length, and removing the alkali in the stretched state and drying without tension. When grey yarn is used in carrying out the pretreatment, the fabric woven from the pretreated yarn can be scoured or kierboiled in the conventional manner prior to resin finishing, without loss of effect subsequent to resin finishing.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a method of preparing crosslinked and wash-wear resin finished cotton textiles. Cotton cellulose crosslinking and wash-wear resin finishing is commonly accomplished by reacting with cotton yarn or fabric a monomer or polymer whose molecules each contain two or more cellulose-etherifying groups. Such cellulose crosslinking or wash-wear resin finishing treatments have wide utility in imparting dimensional stability, resistance to shrinkage, resiliency, wrinkle resistance in the wet and dry states, and smooth drying properties.

The main object of this invention is the prevention of losses of tensile strength hitherto encountered in applications of cellulose crosslinking and/or wash-wear resin treatments to native cotton in the yarn and fabric forms.

A second object of this invention is the prevention of the loss in tearing strength, which was previously obtained in fabrics of native cotton treated with cellulose crosslinking agents and/ or wash-wear resins.

A third object of this invention is to minimize the loss of extensibility encountered in cotton textiles treated with cellulose crosslinking or wash-wear resin finishing agents.

A fourth object of this invention is to greatly increase the tensile and tearing strength of cotton yarns and greige fabrics which have not been subsequently given cellulose crosslinking or wash-wear resin treatments.

A fifth object of this invention is to preserve the softness and suppleness of the cotton while accomplishing the preceding objects.

Other objects of this invention will become apparent in the description that follows.

"ice

It is common knowledge that the use of cellulose cross linking agents or wash-wear resins produces large tearing and tensile strength losses in the treated cotton, These strength losses have hitherto been considered an inherent and inevitable result of the formation of crosslinks in the cellulosic textile. Tovey, Textile Research 1., 31, 185-252 (1961), has exhaustively reviewed the prior literature pertinent to imparting wrinkle resistance to cotton fabrics. He states that strength loss due to creaseproofing is always directly proportional to the degree of recovery conferred by the treatment regardless of the type of reagent used or the degree of cure. Chipalkatti et al., Textile Research J., 33, 282-294 (1963), noted the problem of tensile, tear, and abrasion losses remains still unsolved. Quite a number of research workers seem to have come to the conclusion that such losses are inevitable in these finishes. Nickerson, American Dyestulf Reporter, 39, P46-P5O and P62 (1950) concluded as did Tovey, loc. cit., that the losses are caused by the presence of covalent crosslinks in the cellulose. Garden and Steele, Textile Research 1., 31, -171 (1961), state that attainment of crease recovery by a crosslinking mechanism will always involve loss of strength in cotton. The processes of the present invention yield a form of cotton in which cellulose crosslinking and resin finishing can be carried out with little or no loss of breaking and tearing strength. These processes and the form of cotton so produced are entirely novel, and were not predictable from previous knowledge and art.

Many previous attempts have been made to lessen the harmful effects of cellulose crosslinking and resin finishing of cotton while still retaining the beneficial effects. One method is to mercerize the cotton with concentrated alkali either before or after the cellulose crosslinking or resin finishing step. Mazzeno et al., American Dyestuff Reporter, 46, P719-P724 (1957) Table IV, showed that premercerization, postmercerization, or a combination of the two, gave moderate improvement but still resulted in 24-33% tearing strength loss due to resin treatment, as compared to unmercerized cloth which had not been resin treated. The mercerized, resin-treated fabrics were about 20% stronger than resin-treated cloth which has not been mercerized, so that only 40% of the total tearing strength loss was actually eliminated by these mercerization processes. Reid et al., American Dyestutf Reporter, 52, P946-P947 (1963), Item D of FIG- URE 1, used a combination of slack mercerization and restretching of fabric in their preferred treatment and noted that subsequent resin treatment produced tearing strength losses of 35%, as well as (breaking strength losses of 20,%, as compared to unmercerized fabrics which had not been resin treated. Tovey, loc. cit., further states that crosslinking cotton under tension gives decreased losses of tensile strength, but only at the expense of greater losses in tearing strength and extensibility.

The prior art, as we have indicated, teaches that one of these three properties can be improved at the expense of the remaining two, and that no method has been proposed to prevent the losses in tensile strength and in tearing strength while also minimizing the decrease in extensibility caused by resin finishing. By the processes of our invention we have now accomplished'that which had not been done before. We can produce a fabric with improvement in tearing strength, improvement in breaking strength, and improvement in extensibility.

It is also known that closely woven fabrics are undesirably stiifened by mercerization done in the conventional way, i.e., mercerization of fabric under tension so as to retain approximately the original fabric dimensions. By the processes of our present invention, we can avoid such stiffening effects entirely.

The following sequence of processes represents, in brief,

that which comprises the consecutive steps of our present invention, the preparation of crosslinked or Wash-wear resin finished cotton fabrics with exceptional gains in physical properties:

(a) pretreating the yarn,

(b) weaving the yarn from (a) into fabric, and

(c) reacting the fabric with a cellulose crosslinking,

creaseproofing agent or wash-wear resin.

The yarn pretreatment process (a), which in itself is novel, is preferably carried out on grey 2-ply yarn, but is also applicable to any singles or plied yarn, whether grey, scoured, or kiered. The yarn is soaked for about from 1 to minutes in an aqueous solution of an alkali metal hydroxide, preferably sodium hydroxide, while under little or no tension. This produces shrinkage of the yarn length by about from 10% to 30% due to Swelling. The soak is carried outat about from 3 to +30 C. At about from 3 to +10 C., the concentration of sodium hydroxide needed to give complete swelling is about from 10% to 18% by weight, while at about from 20 to C. the concentration required is about from 18% to 30% by weight. Wetting agents may be present in the alkali solution to increase the rate and extent of penetration of the solution into the yarn. While still wet with the alkali solution, the yarn is restretched by about from 4% to of its length measured in the shrunken state, so as to bring the yarn to within about from 90% to 105% of the original length, and is kept in this alkali-wet, stretched condition for about from 0.5 to 10 minutes. Then, while the alkali-wet yarn is still stretched, it is freed of alkali by washing. If desired, it may be rinsed in dilute acid or in dilute sodium bicarbonate, after which it is again washed. The alkali-free yarn is then dried in the slack condition. The yarn so treated may be scoured or kierboiled without loss of the beneficial effects of pretreatment. Yarns pretreated .=by the processes of our present invention are found to be much stronger than unpretreated yarns. Their X-ray diffraction patterns show they are mainly in the form of cellulose II. Even when treated with a cellulose crosslinking agent, or washwear resin finish, the pretreated yarns remain stronger than unpretreated, uncrosslinked yarn.

In carrying out the yarn pretreatment (a), it is preferable to restretch the yarn while it is wet with the swelling alkali. If the alkali is completely removed prior to yarn restretching, the tension required for restretching is far greater than in the preferred process and must be exerted continuously during subsequent drying, in order to set the yarn at the desired length. This results in an undesirable decrease in extensibility of the yarn. Washing the alkaliwet yarn while applying continuously increasing tension is a variant of the preferred method of restretching and achieves yarn elongation simultaneous with progressing removal of alkali. This method uses relatively low stress, and is like the first method in not requiring tension during drying.

The fabric weaving (b) may be carried out by conventional methods. The pretreated yarn may be used in both the warp and fill direction of the fabric, or pretreated yarn may be used in one direction only and woven with unpretreated yarn in the other fabric direction. The resulting fabric then shows superior strength properties before and after resin treatment, but only in the direction of the pretreated yarn. If grey pretreated yarn is used in weaving the fabric, the cloth may then be scoured or kierboiled in the conventional manner, without loss of effect.

The resulting fabrics have higher tearing and tensile strength than fabrics woven of unpretreated yarn, and when treated with a cellulose crosslinking agent or washwear resin, they remain as strong as ordinary fabric not crosslinked.

The application of cellulose crosslinking agent or Washwear resin treatment, process (c), is carried out in the same manner as on conventional cotton fabrics. In a typical treatment, the fabric is wet with an aqueous solution containing the crosslinking agent or resin, the catalyst and a wetting agent. Fabric softeners and other finishing assistants, or auxiliaries, may be present. The fabric is wrung free of excess solution, and may then be dried prior to heat-curing, or may be heatcured without prior drying. Heat-curing is carried out at IOU- C. for times of 30 seconds to 20 minutes. Typical cross-linking or resin-forming agents used with the fabric produced by the present invention are dimethylolethyleneurea (abbreviated DMEU), tris(1 aziridinyl)phosphine oxide (ab breviated APO), bis(2-hydroxyethyl) sulfone (hereafter called sulfone), and formaldehyde these agents also being well known as creaseproofing agents. Any of the conventional acidic, basic, or metal salt catalysts used with these agents on ordinary fabric may be used on the fabric of the present invention. With DMEU, APO, or formaldehyde, such catalysts as zinc nitrate, magnesium chloride, and tertiary amine hydrochlorides, are found effective in the processes of the present invention. Typical concentrations used in the case of DMEU treatment are 29% DMEU and 0.15-0.65 zinc nitrate. With the sulfone, such catalysts as the alkali metal carbonates and bicarbonates are effective, with sodium carbonate and potassium carbonate being preferred. However, the presence in the treating bath of sodium hydroxide in concentrations as high as 15-30% is to be avoided in carrying out process (c), since the alkali reswells the cotton and alters the orientation already achieved.

The crosslinking or wash-wear finishing of cloth swollen and stretched in the fabric state, or swollen at constant dimensions in the fabric state, gives lower strength retention and extensibility than the crosslinking of cloth woven of yarns swollen and stretched by the methods described herein.

The processes of the present invention can be carried out on any quantity of cotton. The yarn pretreatment (a) may be done on skeins of yarn rotated as an endless belt through the alkali metal hydroxide solution, the restretching being effected by increasing the distance between the two rolls over which the yarn passes. For treating large quantities of yarn, the restretching step may be effected by unwinding the slack-swollen, alkali-wet yarn from a slowly revolving drum onto a second drum of eqaul diameter but which is revolving more rapidly than the first drum.

The following examples illustrate the effectiveness of the processes of the present invention in minimizing strength losses and extensibility losses in cotton yarn subsequently treated with a crosslinking agent or a washwear resin finish. Comparison with known mercerization treatments is made. Also illustrated is the absence of such strength and extensibility losses in fabrics woven from suitably pretreated yarns and given crosslinking 0r wash-wear treatment while in fabric form. Breaking strength and elongation-at-break of fabric were determined by ASTM method D39-49 on strips one-inch in width. Breaking strength values were corrected to the same thread count as the controls. Tearing strength was measured by the Elmendorf method (ASTM D1424-56T). Crease recovery was measured with the Monsanto tester. Yarn breaking strength and elongation-at-break were measured on the Instron tester. The wetting agent used in the alkali metal hydroxide pretreatment of yarn was a cresylic acid type. All parts and percentages are by weight.

Example 1 A 200 yd. skein of 31/2 grey yarn was mercerized at normal length for 5 minutes with 11% NaOH-{4% cresylic wetting agent at 0 C. The caustic was drained and the yarn was washed with cold and then hot tap water, soured with 3% acetic acid, washed again with cold water, and air-dried loose.

Example 2 The procedure of Example 1 was repeated, using 31/2 scoured yarn in place of 31/ 2 grey yarn.

Example 3 The procedure of Example 1 was repeated, using 22% NaOH+l% cresylic wetting agent at 25 C. in place of 11% NaOH+1% cresylic wetting agent at 0 C.

Example 4 The procedure of Example 1 was repeated, using 31/2 scoured yarn in place of 31/2 grey yarn and using 22% NaOH at 25 C. in place of 11% NaOH at 0 C.

6. cresylic wetting agent at C. The yarn was washed with cold and then hot tap water, soured with 3% acetic acid, washed again with cold tap water and air-dried loose.

Example 10 The procedure of Example 9 was repeated using 31/2 scoured yarn in place of 3 1/ 2 grey yarn.

Example 11 TABLE I State 0! Example No. NaOH Yarn Gain in and Resin Cone, Temp., During Brk. Stn, Percent Applied Yarn percent 0 C. Swelling 1 Sta, g. percent N Untreated Grey 630 DMEU 301 -52 Untreated scoured. 721

ME 289 60 826 31 634 1 897 24 604 -16 3 810 29 3-DMEU 668 6 4 Secured..- 22 25 CL 905 25 4DMEU 606 -16 956 52 850 1,033 43 872 21 872 39 80B 28 935 30 765 6 815 30 429 32 10 Secured..- 22 25 887 23 10-DME U 379 -49 1 CL=at constant length; SR=slaek, then restretched; S=slack. 1 Gain in breaking strength based on grev untreated arn.

Example 5 Example 6 The procedure of Example 5 was repeated, using 31/2 scoured yarn in place of 31/ 2 grey yarn.

Example 7 The procedure of Example 5 was repeated, using 22% NaOH at 25 C. in place of 11% NaOH at 0 C.

Example 8 The procedure of Example 5 was repeated, using 31/2 scoured yarn in place of 31/ 2 grey yarn and 22% NaOH at 25 C. in place of 11% NaOH at 0 C.

Example 9 A 200 yd. skein of 3l/2 grey yarn was mercerized with full shrinkage for 5 min. with 22% NaOH+1% The results show that yarn swelled slack in the alkali metal hydroxide and restretched while in the alkali was stronger than either unpretreated yarn, yarn swelled slack, or yarn swelled while being held at constant length. This was true regardless of the temperature or alkali concentration used, for both grey and scoured yarn. This was also true after subsequent crosslinking with DMEU. The yarn swelled slack and then restretched was invariably stronger after DMEU treatment than was the original unswelled and crosslinked yarn. Such yarn was stronger than if pretreated by slack swelling or swelling at constant length, followed by crosslinking. The latter yarns had considerably less strength than unpretreated, uncrosslinked yarn in most instances, particularly if the yarn were scoured.

Example 12 Two 220 yd. skeins of 40/2 grey yarn were swelled in skein form for 4 minutes with 22% NaOH and 1% cresylic wetting agent, to 15% shrinkage, and were stretched back to 91 and 100% of the original skein length. The yarns were washed with cold and then hot tap water, soured with 3% sodium bicarbonate, washed again with cold tap water, and dried loose at 95 C. for 40 minutes. The yarns were resin-finished with DMEU as described above. The results appear in Table II.

TABLE II Each solution also contained 1.5% polyethylene soft- G E ener. Except for runs No. 17 and 18, they also contained 3 133 2 11? 8983 512, .f ttillif 01-05% nonionic Wetting agent. The DMEU, APO, Yarn pretreatment Resin (13-) 199109111; percent and sulfone treating solutions were applied to a wet pick- None 329 up of 70-91%, and the wet fabrics were dried at 85 C. Swelled slack, re- -do 532 62 8.8 for 4 min. They were cured at 150 C. for 4 min. The ,gg i;,}Zi- 464 41 formaldehyde treating solution was applied in the same s way, but the fabric was cured at 155 C. for 3 min. with- None DMEU.-. 181 45 3. 4 d v Swelled,s1aek,re- DMEU 34s 6 5.1 t pr or rylngstr 2 DMEU 435 32 4 8 10 The properties of the treated fabrics appear 1n Table 33,3 3? 56%; l III. Yarn pretreatment by slack swelling and restretching is denoted by SR.

TABLE III Brk. Str. Tear Str. Elong. at Crease recovery (deg) Retn. Retn. break Yarn pre- Level Of -i-F, W+F, -i-F)/ treatment Resin resin 1 Dry Wet percent percent percent Grey fabr'c None 203 179 100 100 12 None 232 189 124 157 15 1.18 270 217 59 36 11 1.13 273 210 112 106 15 1.75 299 259 58 32 1. 62 286 235 113 101 14 0.86 281 262 50 33 11 0. 80 273 253 107 106 14 0.31 269 222 53 40 12 0. 50 271 231 98 105 14 Scoured fabric None 153 213 119 88 13 None 173 209 119 101 19 1.15 271 260 70 49 13 1. 24 275 248 103 105 1.71 233 259 73 44 12 1. 73 293 263 108 99 14 0. 94 288 271 66 46 13 0. 99 288 266 93 100 15 0. 278 260 55 33 13 0. 68 269 248 91 103 15 1 Expressed as percent nitrogen after DMEU or APO treatment, percent sulfur after sulfone treatment, or formaldehyde after formaldehyde treatment.

The pretreated yarns were stronger both before and after resin treatment than was unpretreated, uncrosslinked yarn. The beneficial effects .of pretreatment were obtained regardless of yarn diameter used, as seen by comparison with Example 7 where a different yarn was used. The loss of extensibility caused by DMEU treatment was greatly reduced-by yarn pretreatment.

Example 13 Several pounds of /2 grey yarn were swelled in skein form for 4 min. with 22% NaOH-]1% cresylic wetting agent to 15% shrinkage (46) and stretched back to 91% (49") of the original skein length (54"). The yarn was washed with cold and then hot tap Water, soured with 3% sodium bicarbonate, washed again with cold tap water, and dried loose at 95 C. for 40 min. This mercerized yarn was made into a 44 x 48 sheeting, and part of this fabric was scoured by being heated with 2% NaOH for 90 min. at 100 C., washed and dried, then boiled for 30 min. with 0.25% sodium carbonate 0.5% soap, followed by washing and drying. Control fabric (44 x 48 sheeting) was also made from unpretreated grey yarn. A portion of this fabric was similarly scoured to give a scoured control fabric.

Example 14 Separate portions of each fabric prepared in Example 13 were treated with DMEU, APO, sulfone and formaldehyde. The individual aqueous treating solutions were as follows:

DMEU treatment: 7% DMEU, 0.5% buffered Zinc nitrate APO treatment: 11% APO, 0.77% Zn(BF Sulfone treatment: 9% sulfone 2% Na CO CH O treatment: 7.5% CH O, 2% MgCl -6H O The data for either grey or scoured fabric woven of pretreated yarn show that breaking and tearing strength losses from wash-wear resin treatment were entirely pre- ,vented by yarn pretreatment, taking the strength of grey fabric of unpretreated yarn as the basis of comparison. In many cases the breaking and tearing strength were 2-3 times as great as for control fabric of unpretreated yarn. Improvements of this magnitude have never been previously recorded. This was achieved without sacrifice of the crease recovery normally imparted by the wash-Wear finishing agent. Moreover, the effect was not obtained at any sacrifice in resin content. Invariably the elongation and extensibility of the resin-treated fabric was higher when the fabric was pretreated yarn, than when woven of unpretreated yarn. The results differed but slightly with different cross-linking or wash-wear resin finishing agents, and did not depend on the choice of wash-wear finishing agent used.

Of great significance is the fact that the use of pretreated yarn in weaving a fabric had little effect on the breaking and tearing strength obtained after subsequent scouring of the fabric (experiments 11 and 12 of Table III). Yet when this scoured fabric was given a crosslinking or wash-wear resin treatment, the fabric of pretreated yarn had double or triple the tearing strength of fabric woven with ordinary yarn. It also possessed 50- 60% greater tensile strength than the fabric or ordinary yarn. Thus the high strength obtained after crosslinking is not related to the strength prior to crosslinking, and could not have been predicted from the latter.

We claim: V

1. A process for preparing a crosslinked cotton fabric of increased strength and extensibility, comprising (a) shrinking an original length of cotton yarn by soaking it without tension for about from 1 to 15 minutes in about from 10% to30% by weight aqueous sodium hydroxide at about 3 to +30 C.,

the higher concentrations of sodium hydroxide being used at the higher temperatures;

(b) stretching the alkali-wet cotton yarn by about from 47% to 40%, based on the length of the alkaliwet yarn, so as to bring it to about from 90% to 105% of the original length;

(c) maintaining the yarn in this alkali-wet, stretched condition for about from 0.5 to minutes;

(d) freeing the alkali-wet, stretched yarn of alkali by washing;

(e) drying the resulting alkali-free yarn without tension;

(f) weaving a fabric from the dried, alkali-free yarn;

(g) impregnating the fabric with an aqueous solution containing a crosslinking, creaseproofing agent for cellulose selected from the group consistnig of dimethylolethyleneurea, formaldehyde, tris(1-aziridinyl) phosphine oxide, and bis(2-hydroxyethyl) sulfone, and a catalyst for activating said crosslinking, creaseproofing agent; and

(h) dry-curing the thus-impregnated fabric to effect crosslinking of the cellulose by said crosslinking, creaseproofing agent.

2. The crosslinked cotton fabric produced by the process of claim 1.

3. The process of claim 1 wherein the crosslinking,

creaseproofing agent is dimethylolethyleneurea.

4. The crosslinked cotton fabric produced by the process of claim 3.

5. The process of claim 1 wherein the crosslinking,

creaseproofing agent is formaldehyde,

6. The crosslinked cotton fabric produced by the process of claim 5.

References Cited UNITED STATES PATENTS 600,827 3/1898 Thomas et al. 8125 XR 1,901,095 3/1933 Goldthwait 8125 2,205,120 6/1940 Heberlein et al. 8125 XR FOREIGN PATENTS 4,452 1890 Great Britain.

OTHER REFERENCES Rutherford et al., American Dyestufi' Reporter, Nov. 27, 1961, pp. 23-31 and 63.

Murphy et al., American Dyestuff Reporter, Jan. 20, 1964, pp. (42) 25 and 43 (26).

Marsh John T., Mercerising, 1942, pp. 97, 99-105, 109, and 114-118, D. Van Norstand Co., New York, N.Y.

GEORGE F. LESMES, Primary Examiner J. P. BRAMMER, Assistant Examiner US. Cl. X.R. 

